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THE   AFRICAN   GROUND-PIG                       489

has but a single enamel fold, "whereas in Oa^nnabateo-j/i^/s these
teeth have several enamel folds. The tail, moreover* is but
slightly hairy.
Loncfaeres with eighteen species is another Neotropical genus
allied to the foregoing. Small spines are, as in many of these
genera, intermingled with the fur. This genus has as many as
seventeen dorsal vertebrae, which is an unusually large number.
It. gwianae is known as the <<r Porcupine Rat." Allied genera, also
South American, and without spines in their fur, are Mesomys,
Cerco'mySy and Carterodon.
The South American Thrinacodus is also known by one
species,1 T. aH)icajuday which has rather more than the distal half
of the long tail of a white colour. The fore-feet have four toes.
The ears are broad and short.
Bulb-Fain.. 3. Capromyinae.  A third sub-family of the Octo-
dontidae is formed by the genera JMfyocastor, CfapTomz/s, Plagio-
dontia, and TlirynQmys, which are all Neotropical forms with the
exception of the last, which is African.
Tforynornys (better known perhaps as *Aulacod<us) is a genus
of African Hodent, containing some four species. The best-
known of these is T. swindernianus, the Ground-Hat of West and
South Africa. Its structure has been investigated by Garrod,2
by Tullberg,8 and by myself.4 The fur is mingled with fiattish
bristles ; the tail is moderately long, about half as long as the
body. The fore-feet are five- toed, but the two toes at each end
of the series are quite small. The hind-feet are only four- toed,
the hallux being absent. The claws of the hind-feet are stronger
than, those of the fore-feet. The ears are not long. The limbs
are decidedly short, hence the name of " Ground-Pig M sometimes
applied to this animal. The molars are four in number in both
jaws. The incisors of the upper jaw are twice grooved. There
are thirteen dorsal vertebrae. The length of the small intestine
is 60J- inches, that of the large 49 ; the caecum, is short, being
only 8 inches long. It is a remarkable fact that the acromion
is joined to the rest of the spine of the scapula by a joint.
Myovastor, a name which seems to have the rights of priority
over the more familiar Mtyo%K>tafmus9 applies to a large South
American, aquatic Hodent. The general aspect of the animal
1 Gimther, Proc. Zool. Soc. 1879, p. 144,           a Proc. &aol. Soe. 1873, p. 788.
8 LOG. dt. (on p. 458), p. 123.                   4 Proc. 2faol. /Sfoe, 1892, p. 520.